Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $63.51   13.256%   $71.9289   $71.93   $71.95   $71.90  
  Purchase #2 $206.47   12.265%   $231.7935   $231.79   $231.80   $231.80  
  Purchase #3 $167.48   6.736%   $178.7615   $178.76   $178.75   $178.80  
  Purchase #4 $207.37   12.229%   $232.7293   $232.73   $232.75   $232.70  
  Purchase #5 $203.68   5.507%   $214.8967   $214.90   $214.90   $214.90  
  Purchase #6 $225.76   8.272%   $244.4349   $244.43   $244.45   $244.40  
  Purchase #7 $168.89   10.406%   $186.4647   $186.46   $186.45   $186.50  
  7 purchase totals = $1,243.16       $1,361.0095   $1,361.00   $1,361.05   $1,361.00